High Data Rate (HDR) is an emerging mobile wireless access technology that enables personal broadband Internet services to be accessed anywhere, anytime (see P. Bender, et al., “CDMA/HDR: A Bandwidth-Efficient High-Speed Wireless Data Service for Nomadic Users”, IEEE Communications Magazine, July 2000, and 3GPP2, “Draft Baseline Text for 1xEV-DO,” Aug. 21, 2000). Developed by Qualcomm, HDR is an air interface optimized for Internet Protocol (IP) packet data services that can deliver a shared forward link transmission rate of up to 2.46 Mbit/s per sector using only (1X) 1.25 MHz of spectrum. Compatible with CDMA2000 radio access (TIA/EIA/IS-2001, “Interoperability Specification (IOS) for CDMA2000 Network Access Interfaces,” May 2000) and wireless IP network interfaces (TIA/EIA/TSB-115, “Wireless IP Architecture Based on IETF Protocols,” Jun. 6, 2000, and TIA/EIA/IS-835, “Wireless IP Network Standard,” 3rd Generation Partnership Project 2 (3GPP2), Version 1.0, Jul. 14, 2000), HDR networks can be built entirely on IP technologies, all the way from the mobile Access Terminal (AT) to the global Internet, thus taking full advantage of the scalability, redundancy and low-cost of IP networks.
An EVolution of the current 1xRTT standard for high-speed data-only (DO) services, also known as the 1xEV-DO protocol has been standardized by the Telecommunication Industry Association (TIA) as TIA/EIA/IS-856, “CDMA2000 High Rate Packet Data Air Interface Specification”, 3GPP2 C.S0024-0, Version 4.0, Oct. 25, 2002, which is incorporated herein by reference. Revision A to this specification has been published as TIA/EIA/IS-856, “CDMA2000 High Rate Packet Data Air Interface Specification”, 3GPP2 C.S0024-A, Version 1.0, March 2004, Ballot Resolution, but has yet not been adopted. Revision A is also incorporated herein by reference.
A 1xEV-DO radio access network (RAN) includes access terminals in communication with radio nodes over airlinks. Each access terminal may be a laptop computer, a Personal Digital Assistant (PDA), a dual-mode voice/data handset, or another device, with built-in 1xEV-DO support. The radio nodes are connected to radio node controllers over a backhaul network that can be implemented using a shared IP or metropolitan Ethernet network which supports many-to-many connectivity between the radio nodes and the radio node controllers. The radio access network also includes a packet data serving node, which is a wireless edge router that connects the radio access network to the Internet.
Typically, each radio node controller controls 25-100 radio nodes and each radio node supports 1-4 carriers each of 1.25 MHz of bandwidth. The geographic area of the radio access network that is served by any given radio node is referred to as a cell. Each cell can be divided into multiple sectors (typically 3 or 6).
Access terminals in a 1xEV-DO radio access network periodically send route update messages to the network. Each route update message identifies the sectors that are “visible” to the access terminal. The sector identification enables the radio access network to keep track of the access terminal's approximate location within the footprint of the network and to maintain the airlink as the access terminal moves between the coverage areas of different sectors.
When the radio access network has to page an access terminal to notify it of an incoming call, the network selects a set of sectors to page the terminal on.
One selection method known as “flood paging” involves selecting all of the sectors in the radio access network. The flood paging method covers a large paging area often at significant expense cost-wise.
Another selection method known as “selective paging” involves selecting a subset of the sectors in the radio access network. In one example, the radio access network reduces the size of the paging area by selecting only those sectors that are within a specified distance (referred to in the IS-856 specification as a “RouteUpdateRadius” or “RUR”) of the sector (“paging reference sector”) from which the access terminal last sent a route update message. The shape of such a paging area is a circle on the surface of the earth, in which the paging reference sector's longitude and latitude co-ordinates represents the center of the circle and the specified distance or the RUR represents the radius of the circle. To determine whether a sector (“sector under test”) in the network is within a circular paging area of a paging reference sector, the radio access network uses the following formula provided in the IS-856 to calculate the distance r between the paging reference sector and the sector under test:
  r  =      ⌊                                                      [                                                (                                                            x                      c                                        -                                          x                      L                                                        )                                ×                                  cos                  ⁡                                      (                                                                  π                        180                                            ×                                                                        y                          L                                                14400                                                              )                                                              ]                        2                    +                                    [                                                y                  c                                -                                  y                  L                                            ]                        2                              16        ⌋  
where (xC,yC) represents the longitude and latitude co-ordinates of the paging reference sector, and (xL,yL) represents the longitude and latitude co-ordinates of the sector under test. If the computed value of r is less than RUR, the sector under test is inside the circular paging area and is selected by the radio access network for use in paging the access terminal for an incoming call.
In certain cases, each of the sectors identified by an access terminal in its route update message can be considered a paging reference sector that contributes its own paging area. At the time of paging, a radio access network that uses the above-identified formula to determine whether an individual sector under test is within a paging area of a given paging reference sector has to perform a series of calculations per paging reference sector to identify all of the sectors that are within a union of the paging areas associated with the multiple paging reference sectors. In certain cases in which an identified sector is within the paging areas of more than one paging reference sector, an access terminal may be paged multiple times by a single sector.
To avoid having to do the processing intensive calculations associated with the above-identified formula on-the-fly at the time of paging, the network may pre-determine and store the sectors to be paged for each sector that can be a paging reference sector. In a distributed system (e.g., a multi-chassis system), updates to such stored information resulting from changes to the set of sectors can be costly and vulnerable to card failures.